1. Field of the Invention
The invention relates to downhole tools used in oil and gas wellbores. More particularly, but not by way of limitation, the invention relates to downhole apparatus used anchoring a work string to a packer as well as for releasing the anchoring device from the packer.
2. Description of the Prior Art
In the past, packers such as the Halliburton Drillable-Test-Treat and Squeeze Packers have been utilized in a number of different applications in the oil and gas industry. Other packers, such as that disclosed in U.S. Pat. No. 4,151,875 to Sullaway, assigned to the assignee of the present invention, also contain similar features to the Drillable-Test-Treat and Squeeze Packers.
Before beginning test, treat or squeeze operations, the operator is required to sting into the top of the packer with the workstring. This is also referred to as anchoring into the packer. After the cycle, the anchoring apparatus is pulled out of the wellbore.
Next, it necessary to retrieve the packer from the wellbore. Basically, there are two methods utilized. The first method utilizes the step of drilling the packer out with a rock bit. With this particular method, the packer is literally drilled out of the wellbore. The second method comprises milling over a portion of the packer and utilizing an overshot to pick-out the packer.
The present invention allows for anchoring a stinger assembly to the packer and subsequently retrieving the stinger assembly. A common problem encountered while releasing from the packer is for the stinger assembly to become stuck. Once the stinger assembly becomes stuck, many times the only way of retrieving the work string is to part the work string at some point above the stinger, thus leaving a portion of the work string above the packer in the wellbore. This situation, as will be appreciated by those skilled in the art, presents major difficulties.
U.S. Pat. No. 5,207,274, assigned to the assignee of the present invention, provides a tool that will easily and effectively anchor a stinger assembly to a downhole packer during drill, test, treat or squeeze operations. The tool provides for an emergency release in the event the anchoring tool becomes stuck in the packer. This is accomplished with a stinger with a collet thereon having collet fingers which ratchet into threads in the packer. Upon applying tension to the work string, a shear ring is moved up and under the collet fingers to sufficiently support them so that they will stay locked in the packer. Upon completion of the job, rotation of the work string causes the collet fingers to rotate out of the mandrel and free the stinger from the packer. If the collets freeze up or otherwise become locked in the threads, a predetermined amount of tension on the work string will shearably release the shear ring, thereby removing support from the collet fingers. When the shear ring support is removed, the collet fingers will simply pop out of the packer due to the design of the threads.
During normal operation of this prior apparatus, torque is transmitted to the collet fingers by a splined extension on the shear ring. Because the shear ring is shearably attached, it will provide torque limitation by releasing when sufficient torque is applied thereto. A potential problem is that sufficient torque may be applied prematurely to the splined extensions such that the shear ring is inadvertently sheared, thereby causing premature disengagement of the stinger from the packer.
The present invention solves this problem by modifying the previous apparatus such that the splines are relocated to a separate load or spline ring rather than on the shear ring. In this way, any torque load may be applied without danger of premature releasing of the shear ring.